When the moon is high in the sky, it creates bulges in the planet's atmosphere that creates imperceptible changes in the amount of rain that falls below.
New University of Washington research to be published in Geophysical Research Letters shows that the lunar forces affect the amount of rain - though very slightly.
Satellite data over the tropics, between 10 degrees S and 10 degrees N, shows a slight dip in rainfall when the moon is directly overhead or underfoot. The top panel shows the air pressure, the middle shows the rate of change in air pressure, and the bottom shows the rainfall difference from the average. The change is 0.78 micrometers, or less than one ten thousandth of an inch, per hour.
Credit: Tsubasa Kohyama/University of Washington
"As far as I know, this is the first study to convincingly connect the tidal force of the moon with rainfall," said corresponding author Tsubasa Kohyama, a UW doctoral student in atmospheric sciences.
Kohyama was studying atmospheric waves when he noticed a slight oscillation in the air pressure. He and co-author John (Michael) Wallace, a UW professor of atmospheric sciences, spent two years tracking down the phenomenon.
Air pressure changes linked to the phases of the moon were first detected in 1847,and temperature in 1932, in ground-based observations. An earlier paper by the UW researchers used a global grid of data to confirm that air pressure on the surface definitely varies with the phases of the moon.
"When the moon is overhead or underfoot, the air pressure is higher," Kohyama said.
Their new paper is the first to show that the moon's gravitational tug also puts a slight damper on the rain.
When the moon is overhead, its gravity causes Earth's atmosphere to bulge toward it, so the pressure or weight of the atmosphere on that side of the planet goes up. Higher pressure increases the temperature of air parcels below. Since warmer air can hold more moisture, the same air parcels are now farther from their moisture capacity.
"It's like the container becomes larger at higher pressure," Kohyama said. The relative humidity affects rain, he said, because "lower humidity is less favorable for precipitation."
Kohyama and Wallace used 15 years of data collected by NASA and the Japan Aerospace Exploration Agency's Tropical Rainfall Measuring Mission satellite from 1998 to 2012 to show that the rain is indeed slightly lighter when the moon is high. The change is only about 1 percent of the total rainfall variation, though, so not enough to affect other aspects of the weather or for people to notice the difference.
"No one should carry an umbrella just because the moon is rising," Kohyama said. Instead, this effect could be used to test climate models, he said, to check if their physics is good enough to reproduce how the pull of the moon eventually leads to less rain.
Wallace plans to continue exploring the topic to see whether certain categories of rain, like heavy downpours, are more susceptible to the phases of the moon, and whether the frequency of rainstorms shows any lunar connection.
The research was funded by the National Science Foundation, the Tanaka Ikueikai Scholarship Society, and the Iizuka Takeshi Scholarship Foundation.
For more information, contact Kohyama at firstname.lastname@example.org. Wallace is traveling out of the country through March.
Hannah Hickey | EurekAlert!
In times of climate change: What a lake’s colour can tell about its condition
21.09.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)
Did marine sponges trigger the ‘Cambrian explosion’ through ‘ecosystem engineering’?
21.09.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
21.09.2017 | Physics and Astronomy
21.09.2017 | Life Sciences
21.09.2017 | Health and Medicine